Once you have worked out any story kinks in your Rough Board Revisions use the Final or Clean-up pass to refine your drawings, add tone to strengthen compositions and fill in any needed panels to communicate story flow and camera moves.  This is also where all camera notations are clearly communicated. 

If you are not already working digitally you may want to consider it at this point.  While old school story artists use registered paper (taking advantage of the animation disc/light table) most of you will be redrawing directly over your scans in Photoshop.  Either method will allow you to refine your images, add tone, and solve issues around having to repeat backgrounds as each shot may require multiple panels to convey action.  At this point you should be working in layered drawings that will most easily translate into a Story Reel.


Storyboards from Blue Sky's Scrat

Storyboard Clean-ups from The Temptation of Brother Thomas